primary microcephaly
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2023 ◽  
Vol 83 ◽  
Author(s):  
T. Batool ◽  
S. Irshad ◽  
K. Mahmood

Abstract Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder characterized by a congenitally reduced head circumference (-3 to -5 SD) and non-progressive intellectual disability. The objective of the study was to evaluate pathogenic mutations in the ASPM gene to understand etiology and molecular mechanism of primary microcephaly. Blood samples were collected from various families across different remote areas of Pakistan from February 2017 to May 2019 who were identified to be affected with primary microcephaly. DNA extraction was performed using the salting-out method; the quality and quantity of DNA were evaluated using spectrophotometry and 1% agarose gel electrophoresis, respectively in University of the Punjab. Mutation analysis was performed by whole exome sequencing from the Cologne Center for Genomics, University of Cologne. Sanger sequencing was done in University of the Punjab to confirm the pathogenic nature of mutation. A novel 4-bp deletion mutation c.3877_3880delGAGA was detected in exon 17 of the ASPM gene in two primary microcephaly affected families (A and B), which resulted in a frame shift mutation in the gene followed by truncated protein synthesis (p.Glu1293Lysfs*10), as well as the loss of the calmodulin-binding IQ domain and the Armadillo-like domain in the ASPM protein. Using the in-silico tools Mutation Taster, PROVEAN, and PolyPhen, the pathogenic effect of this novel mutation was tested; it was predicted to be “disease causing,” with high pathogenicity scores. One previously reported mutation in exon 24 (c.9730C>T) of the ASPM gene resulting in protein truncation (p.Arg3244*) was also observed in family C. Mutations in the ASPM gene are the most common cause of MCPH in most cases. Therefore, enrolling additional affected families from remote areas of Pakistan would help in identifying or mapping novel mutations in the ASPM gene of primary microcephaly.


2021 ◽  
Vol 35 (23-24) ◽  
pp. 1551-1578
Author(s):  
Thao P. Phan ◽  
Andrew J. Holland

Primary microcephaly is a brain growth disorder characterized by a severe reduction of brain size and thinning of the cerebral cortex. Many primary microcephaly mutations occur in genes that encode centrosome proteins, highlighting an important role for centrosomes in cortical development. Centrosomes are microtubule organizing centers that participate in several processes, including controlling polarity, catalyzing spindle assembly in mitosis, and building primary cilia. Understanding which of these processes are altered and how these disruptions contribute to microcephaly pathogenesis is a central unresolved question. In this review, we revisit the different models that have been proposed to explain how centrosome dysfunction impairs cortical development. We review the evidence supporting a unified model in which centrosome defects reduce cell proliferation in the developing cortex by prolonging mitosis and activating a mitotic surveillance pathway. Finally, we also extend our discussion to centrosome-independent microcephaly mutations, such as those involved in DNA replication and repair.


2021 ◽  
Vol 38 (1) ◽  
Author(s):  
Ehtisham ul Haq Makhdoom ◽  
Haseeb Anwar ◽  
Shahid Mahmood Baig ◽  
Ghulam Hussain

Background & Objectives: Primary Microcephaly (MCPH) is a rare neurogenetic disease, manifesting congenitally reduced head circumference and non-progressive intellectual disability (ID). To date, twenty-eight genes with biallelic mutations have been reported for this disorder. The study aimed for molecular genetic characterization of Pakistani families segregating MCPH. Methods: We studied two unrelated consanguineous families (family A and B) presenting >2 patients with diagnostic symptoms of MCPH, born to asymptomatic parents. We employed whole-exome sequencing (WES) of probands to find putative causal mutations. The candidate variants were further confirmed and analyzed for co-segregation by Sanger sequencing of all available members of each family. This study was conducted at Government College University, Faisalabad, Pakistan, and Cologne Center for Genomics (CCG), University of Cologne, Germany; during 2017-2020. Results: We identified a novel homozygous variant c.10097_10098delGA, p.(Gly3366Glufs*19) in exon 26 of ASPM gene in family A which presents with moderate intellectual disability, speech impairment, visual abnormalities, seizures, and ptyalism. Family B was found to segregate nonsense, homozygous variant c.448C>T p.(Arg150*) in CDK5RAP2. The patients also exhibited mild to severe seizures without ptyalism that has not been previously reported in patients with mutations in the CDK5RAP2 gene. Conclusion: We report a novel mutation in ASPM and ultra-rare mutation in the CDK5RAP2 gene, both causing primary microcephaly. The study expands the mutational spectrum of the ASPM gene to 212, and also adds to the clinical spectrum of CDK5RAP2 mutations. It also demonstrated the utility of WES in the investigation and genetic diagnosis of genetically heterogeneous disorders like MCPH. These findings would aid in diagnostic and preventive strategies including carrier screening, cascade testing, and genetic counselling. doi: https://doi.org/10.12669/pjms.38.1.4464 How to cite this:Makhdoom EH, Anwar H, Baig SM, Hussain G. Whole exome sequencing identifies a novel mutation in ASPM and ultra-rare mutation in CDK5RAP2 causing Primary microcephaly in consanguineous Pakistani families. Pak J Med Sci. 2022;38(1):---------.  doi: https://doi.org/10.12669/pjms.38.1.4464 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


2021 ◽  
Author(s):  
Ipek Ilgin Gonenc ◽  
Nursel Huriye Elcioglu ◽  
Carolina Martinez Grijalva ◽  
Seda Aras ◽  
Nadine Grossmann ◽  
...  

Bloom syndrome (BS) is an autosomal recessive disease with characteristic clinical features of primary microcephaly, growth deficiency, skin lesions, cancer predisposition, and immunodeficiency. Here, we report the clinical and molecular findings of eight patients from six families diagnosed with BS. We identified causative mutations in all families, three different homozygous mutations in BLM and one causative homozygous mutation in RMI1. The homozygous c.581_582delTT (p.Phe194*) and c.3164G>C (p.Cys1055Ser) mutations in BLM have already been reported in BS patients, while the c.572_573delGA (p.Arg191Lysfs*4) is novel. Interestingly, whole-exome sequencing revealed a homozygous loss-of-function mutation in RMI1 in two BS patients of a consanguineous Turkish family. All BS patients had primary microcephaly, intrauterine growth delay, and short stature, presenting the phenotypic hallmarks of BS. However, a narrow face, skin lesions, and upper airway infections were observed only in some of the patients. Overall, patients with homozygous BLM mutations had a more severe BS phenotype compared to patients carrying the homozygous RMI1 mutation, especially in terms of immunodeficiency and associated recurrent infections. Low-level immunoglobulins were observed in all BLM-mutated patients, emphasizing the immunodeficiency profile of the disease, which should be considered as an important phenotypic characteristic of BS, especially in the current Covid-19 pandemic era.


2021 ◽  
Author(s):  
Khaled Ramadan Ferih ◽  
Ahmed Adel Elsabagh ◽  
Sami Ismail Zaqout ◽  
Angelika Krajewski

Autosomal recessive primary microcephaly (MCPH) consists of a group of disorders characterized by microcephaly and intellectual disability. This study is essential to complement previous findings of MCPH as it helps clarify the role of different genes and proteins involved in the underlying pathophysiology of MCPH. To date, 27 different mutations have been identified. This study defines a number of changes in gene expression occurring in MCPH. This helps deepen our understanding of the effect of MCPH mutations on gene expression. This study also shows the functions of proteins that increase, are unaffected or become dysfunctional due to MCPH. We identified a marked reduction of about 30 proteins with vital roles in several processes including cell cytoskeleton dynamics, cell cycle progression, ciliary functions, and apoptosis. We used Cdk5rap2 (Hartwig’s anemia mice (an/an)), which is a model that closely represents MCPH3. Gel electrophoresis was utilized in order to separate brain proteins. Fixation and protein identification was then done in order to detect changes in the level of the tested proteins


2021 ◽  
Author(s):  
Ipek Ilgin Gönenc ◽  
Alexander Wolff ◽  
Julia Schmidt ◽  
Arne Zibat ◽  
Christian Müller ◽  
...  

AbstractBloom syndrome (BS) is an autosomal recessive disease clinically characterized by primary microcephaly, growth deficiency, immunodeficiency, and predisposition to cancer. It is mainly caused by biallelic loss-of-function mutations in the BLM gene, which encodes the BLM helicase, acting in DNA replication and repair processes. Here, we describe the gene expression profiles of three BS fibroblast cell lines harboring causative, biallelic truncating mutations obtained by single-cell (sc) transcriptome analysis. We compared the scRNA transcription profiles from three BS patient cell lines to two age-matched wild-type controls and observed specific deregulation of gene sets related to the molecular processes characteristically affected in BS, such as mitosis, chromosome segregation, cell cycle regulation, and genomic instability. We also found specific upregulation of genes of the Fanconi anemia pathway, in particular FANCM, FANCD2, and FANCI, which encode known interaction partners of BLM. The significant deregulation of genes associated with inherited forms of primary microcephaly observed in our study might explain in part the molecular pathogenesis of microcephaly in BS, one of the main clinical characteristics in patients. Finally, our data provide first evidence of a novel link between BLM dysfunction and transcriptional changes in condensin complex I and II genes. Overall, our study provides novel insights into gene expression profiles in BS on a single-cell level, linking specific genes and pathways to BLM dysfunction.


2021 ◽  
Author(s):  
Sonja Neuser ◽  
Ilona Krey ◽  
Annemarie Schwan ◽  
Tobias Bartolomaeus ◽  
Jan Henje Doering ◽  
...  

Biallelic PNKP variants cause heterogeneous disorders ranging from neurodevelopmental disorder with microcephaly/seizures to adult-onset Charcot-Marie-Tooth disease. To date, only postnatal descriptions exist. We present the first prenatal diagnosis of PNKP-related primary microcephaly. Detailed pathological examination of a male fetus revealed micrencephaly with extracerebral malformations and thus presumed syndromic microcephaly. A recessive disorder was suspected because of previous pregnancy termination for similar abnormalities in a sibling fetus. Prenatal trio exome sequencing identified compound-heterozygosity for the PNKP variants c.498G>A, p.[(=),0?] and c.302C>T, p.(Pro101Leu). Segregation confirmed both variants in the sibling fetus. Through RNA analyses, we characterized skipping of exon 4 affecting the PNKP Forkhead-associated (FHA) and Phosphatase domains (p.Leu67_Lys166del) as the predominant effect of the c.498G>A variant. We retrospectively investigated two unrelated individuals diagnosed with biallelic PNKP-variants to compare prenatal/postnatal phenotypes. Both carry the same splice-donor variant c.1029+2T>C in trans with a variant in the FHA domain (c.311T>C, p.(Leu104Pro) and c.151G>C, p.(Val51Leu), respectively). RNA-seq showed complex splicing events for c.1029+2T>C and c.151G>C. Computational modelling and structural analysis revealed significant clustering of missense variants in the FHA domain, with some variants potentially generating structural damage. Our detailed clinical description extends the PNKP-continuum to the prenatal stage. Investigating possible PNKP-variant effects using RNA and structural modelling, we highlight the mutational complexity and exemplify a framework for variant characterization in this multi-domain protein.


Author(s):  
Lyse Ruaud ◽  
Séverine Drunat ◽  
Monique Elmaleh‐Bergès ◽  
Anais Ernault ◽  
Sophie Guilmin Crepon ◽  
...  

2021 ◽  
pp. 1-8
Author(s):  
Ayberk Türkyılmaz ◽  
Safiye Gunes Sager

Autosomal recessive primary microcephaly (MCPH) is a uncommon disorder due to congenital deficiency in the development of the cerebral cortex, characterized by a head circumference below 2 SD. MCPH is a group of diseases with genetic heterogeneity and has been reported by the Online Mendelian Inheritance In Man® (OMIM) database and associated with 25 different genes. It is known that MCPH cases are most frequently associated with abnormal spindle-like, microcephaly-associated (<i>ASPM</i>) gene mutations. The ASPM protein consists of an N-terminal 81 IQ (isoleucine-glutamine) domain, a calponin-homology domain, and a C-terminal domain. It interacts with calmodulin and calmodulin-related proteins via the IQ domain and acts as a part in mitotic spindle function. The basic characteristics of cases with <i>ASPM</i> gene mutations are microcephaly (below <b>−</b>3 SD) present before 1 year of age, intellectual disability, and the absence of other congenital anomalies. Macroscopic organization of the brain is preserved in cases with <i>ASPM</i> mutation, and a decrease in brain volume, particularly gray matter volume loss and a simplified gyral pattern are observed. Cortical migration defects are a very rare finding in patients with <i>ASPM</i> mutations. In the present study, we aimed to discuss the clinical and genetic findings in 2 cases with cortical dysplasia in which truncated variants in the <i>ASPM</i> gene were detected, particularly in terms of genotype-phenotype correlation in comparison with the literature.


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